Coupling for outer surface engagement of polymeric pipe

ABSTRACT

A coupling for engagement with the outer surface of a polymeric pipe, having a sub-assembly of a compression sleeve (24), a resilient gasket ring (18) permanently attached to the inner end of the compression sleeve (24), a gripping member (25), and a nut (30). The gasket ring (18) encounters an abutment in a socket (17) in the body (12) as the nut (30) is tightened, and further tightening of the nut (30) radially compresses the gripping member (25) so that its inwardly directed barbed projections (26) engage the outer surface of a pipe (11) to which the coupling is attached. The end of pipe (11) is freely insertable through the gripping member (25) and sleeve (24), and into the socket (17) in the body (12). There are also provided abutment surfaces within the body coupling and the nut which abut inner and outer surfaces (34, 35) of a flange outstanding from the outer end of the compression sleeve (24). Also disclosed is an embodiment with a transition spigot (46) having a barbed tail inserted into an end of a pipe enabling the coupling to accommodate a range of similar but different diameter pipes.

This invention relates to a coupling which is suitable for engaging theouter surface of a polymeric pipe, without it being always essential foran internal sleeve to be inserted into the pipe.

BACKGROUND OF THE INVENTION

In our Australian Patent 534452 entitled "Improvements in PipeFittings", a pipe fitting was described and illustrated wherein a sleevewas provided with a tail for insertion into a pipe, and there was alsoprovided a compression ring having serrations thereon for compressingthe end of the pipe against the outer surface of the tail, the tailpreferably having serrations thereon. There was also provided a sealingring of elastomeric material which engaged between the sleeve and abody, and the assembly was achieved by means of a sleeve nut which had atapered inner surface which engaged a complementary male tapered outersurface of the compression ring. The sleeve was also provided with apair of spaced peripheral flanges, one bearing against the resilientgasket ring and the other bearing against one end of the compressionring, so that the axial distance between those two rings did not varyupon tightening of the nut.

The pipe fittings described in the aforesaid specification have provento be very successful, both technically and commercially. Failure isalmost unknown and in some areas of the world fittings made inaccordance with that specification are sold in greater numbers thantheir competitor's fittings.

A practical problem which is frequently encountered with fittings madein accordance with said patent 534452 (and other fittings in commonuse), is that the nut and compression ring needs to be positioned over apipe end before tail of the sleeve is inserted. If either the nut orring is inadvertently omitted, the tail usually cannot be withdrawn(because of barbed serrations), and it becomes necessary to cut thepipe.

The main object of this invention is therefore to provide improvementswhereby the body, nut and gripping member (compression ring) cancomprise a preliminary assembly through which can be inserted a pipe,which can simply be secured by tightening the nut, or removed byunscrewing.

Further, there is a need for a fitting which does not always have a tailinserted within a pipe, thereby avoiding interference with fluid flowwithin the pipe, and which takes advantage of the existence of anacceptable standard of accuracy of diameter of some polymeric pipes. Forexample the variation in outer diameter of a 50 mm pipe is likely to beless than 0.5 mm (0.020"). This makes it possible to have a couplingwhich engages only the outer surface of a pipe, and which restrains apipe against leakage and against axial displacement, relying upon thestiffness of the pipe itself.

It is known that there exist fittings each comprising an outercylindrical body which does not have any sleeve nut, but has an innertaper surface which converges in the direction of the pipe to which itis to be attached, the inner taper surface co-operating with acompression sleeve having a sawtooth profile to grip the outer surfaceof a pipe, and the pipe is merely pushed into the end of the body andthrough the taper sleeve and pulled outwardly again, causing thesawtooth projections to firmly grip the surface of the pipe, and retainthe pipe in position. This is a simple and inexpensive fitting, butsometimes disassembly is difficult to achieve.

In some prior art fittings, it is sometimes necessary to chamfer a pipeend before insertion into the fitting, or lubricate a pipe end, or both,and this is quite inconvenient. Further, manual insertion is sometimesnecessary to effect a seal between pipe and fitting, and this caninvolve distortion of a gasket ring, by application of direct axialforce.

Another of the objects of this invention is to provide a coupling whichcomprises a nut which positively both compresses a gasket ring against asurface to effect a seal against leakage, and which limits the amount ofgripping of the pipe, both to a predetermined level, thereby providingmeans which prevents excessive distortion of the resilient gasket ring,and also controls the degree of compression of a gripping member onto apipe. Without such limiting means, a possibility exists of destructionof the split ring. It is known in the art that split rings of the"finger" type can be destroyed upon excessive forces being imparted.

A further difficulty which may conceivably be encountered with fittingsof the sleeve type which contain both resilient gaskets and split ringswith sawtooth profiles, is that although supplied in relaxed state, theycan be tightened by hand inadvertently and thereby force the resilientgasket ring into a tapered socket from which it is not readilywithdrawn. Such fittings if again relaxed, leave the gasket rings inposition and there is always a danger of damage with consequentialsubsequent leakage if the gasket rings are hooked out or pushed out witha sharp instrument. A further object of the invention is to providemeans whereby the resilient gasket ring will be withdrawn uponunscrewing of the nut.

A still further object of the invention is to have an arrangementwhereby the degree of compression of the resilient gasket ring andgripping member with inwardly directed barb projections is controlled bythe dimensions of the components of the coupling to be effective withina range of tolerance of diameter of the pipe with which the coupling isto be used, ensuring proper sealing of the resilient gasket ring andproper gripping of the pipe even when the pipe is on "bottom tolerance",but also assuring that there is unlikely to be damage to the resilientgasket ring, to the gripping member or to the pipe due to overtightening of a sleeve nut.

Situations arise whereby pipes produced to different standards(Australian, I.S.O., British, American etc) vary by relatively smallamounts in their bore, but the outer diameters are not always compatiblewith a fitting made to a different standard, and a still further objectof the invention is to provide a transition means between a pipe and afitting, so as to reduce inventory costs, one standard size fitting thenbeing useable with pipes of similar but not identical size made todifferent standards by a mere selection of inexpensive transition means.

PRIOR ART

The closest prior art known to the applicant is the U.S. Pat. No.4043576in the name of REICH and LEHMANN of Switzerland and assigned toGEORGE FISCHER AKTIENGESELLSCHAFT.

In that specification, there was provided a coupling for a smooth pipewhich included a body, a nut threaded onto the body, a gasket inside thebody and a thrust and locking ring structure within and between thathousing and sleeve nut. The body had an inner tapered surface tocompress the gasket. When the nut was threaded onto the housing, thelocking ring structure was moved axially by an abutment shoulder on thenut to compress the gasket through a compression sleeve to a degreewhich was predetermined, and the nut subsequently deformed the tonguesof the locking ring structure to grip the pipe.

BRIEF SUMMARY OF THE INVENTION

In this invention, however, there is provided a gripping member and asub-assembly of compression sleeve and resilient gasket ring permanentlyattached to the inner end of the compression sleeve. A pipe end isfreely insertable through the sub-assembly and into a socket in the bodyof the coupling. The gasket ring encounters an abutment in its socket inthe body as the nut is tightened, and further tightening of the nutradially compresses the gripping member so that its inwardly directedbarbed projections engage the outer surface of a pipe to which thecoupling is attached. There are also provided abutment surfaces withinthe body of the coupling and the nut which abut inner and outer surfacesof a flange outstanding from the outer end of the compression sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

Two embodiments of the invention and described hereunder in some detailwith reference to, and are illustrated in, the accompanying drawings, inwhich:

FIG. 1 is a central elevational section which shows a pipe end insertedthrough a sub-assembly comprising a nut, gripping member and sleeve, andinto a socket in the body of a fitting;

FIG. 2 is a similar section showing the configuration of components whenthe nut is tightened onto the body;

FIG. 3 is a half section elevation similar to FIG. 1, showing thearrangement, before its insertion, when the pipe end is an end of atransition spigot; and

FIG. 4 is a section similar to FIG. 3, but showing the configurationwhen the nut is tightened.

In the first embodiment of FIGS. 1 and 2, a coupling 10 for outersurface engagement of a polymeric pipe 11 comprises a body 12 which hasan internal abutment shoulder 13 which is abutted by the end of pipe 11when inserted into the coupling as shown in FIG. 1. The body 12 has amale thread 14, and between the outer end 15 and the shoulder 13 is agenerally annular planar surface 16 which constitutes an abutmentsurface of a socket 17 for a resilient gasket ring 18, abutment shoulder13 of the socket 17 being the inner end of the socket, the socket 17also having two cylindrical intermediate and axially outer walls 19 and20 separated by a step 21 (three diameters in all), the diameter of theouter wall 20 exceeding that of the inner wall 19.

Surrounding the pipe 11 is a compression sleeve 24 which carries theresilient gasket ring 18 on its inner end, being fused, bonded, orotherwise affixed to the end of the compression sleeve 24. This couldalternatively be engaged by a mechanical tongue and groove or otherwiseaffixed on the face end of the sleeve 24, and the outer diameter ofgasket ring 18 is less than the diameter of outer wall 20 but greaterthan diameter of intermediate wall 19, so that the compression sleevecan be readily inserted into the body 12 with the gasket ring 18 beingfreely movable within the wall 20 but requiring compression by axialmovement of compression sleeve 24 to enter the wall 19.

Adjacent but axially outwardly of sleeve 24 is a gripping member 25having radially inwardly but axially spaced barb projections 26, andhaving an outwardly converging tapered surface 27. The gripping member25 must be radially deformable, and thereby circumferentiallydeformable, and is typically a split ring.

The nut 30 is provided with a tail 31 having an outwardly converginginner tapered surface 32 the included angle of which is approximatelythe same as the tapered surface 27 of the gripping member 25, andinwardly from the outer end of tail 31 there is an annular planarshoulder 33 which, upon tightening of the nut 30, will bear against endsurface 34 of compression sleeve 24.

The annular surface 35 of the flange at the outer end of sleeve 24 isspaced axially inwardly a short distance from the surface 34.

Assuming that the pipe 11 is inserted into the socket 17 of the couplingas shown in FIGS. 1 and 2, initial tightening of the nut 30 on the body12 will not cause abutment of shoulder 33 with annular surface 34 of thesleeve 24. The inner end of the gripping member 25 is loosely containedwithin a recess 36 in the outer end of sleeve 24, and the gasket ring18, sleeve 24 and gripping member 25 move in together with the nut 30since there is a clearance of all portions of the coupling around thepolymeric pipe 11 when it is first inserted. However, after the nut 30travels a short axial distance inwardly the gasket ring 18 isintercepted by the step 21 and will not pass that step until compressed.Continued movement of the nut therefore causes a small axially inwardmovement of the sleeve 24 and the gripping member 25, and must beaccommodated by the sliding of inner surface 32 over the outer taperedsurface 27, in turn causing the barb projections 26 of the grippingmember 25 to engage the outer surface of pipe 11. Tightening of the nut30 also brings the shoulder 33 into abutment with the annular surface 34of compression sleeve 24 and progresses the sleeve 24 axially inwardly,causing sufficient compression of the gasket ring 18 for it to enter theinner smaller diameter intermediate portion 19 of the socket 17. Thesocket is of such dimension that the gasket ring 18 effects asatisfactory seal between the body 12 and the pipe 11, and this isfurther enhanced when the nut 30 is fully tightened so that the twosurfaces of the sleeve 24 respectively lie in abutment with the outerend 15 of the body 12 and the shoulder 33 as shown in FIG. 2. At thislocation, further compression of the resilient gasket ring 18 results ina seal which is effective against very high pressures. However,rotational twisting of the gasket ring 18 is substantially avoided, asis rotational twisting of the gripping member 25. Since the nut cannotbe progressed any further inwardly, the compression of both the rings 18and 25 is controlled to lie within the range dictated by the diameter ofthe pipe 11.

If the pipe 11 is not inserted into the body 12 and the nut is screwedforwardly, the pipe will not be able to be forced inwardly to the bodyunless the nut is screwed back to its loose state.

When the nut is screwed back the compression sleeve is also pulled backdue to a loose engagement of the reverse tapered surfaces 40 ofcompression sleeve 24 and 41 of sleeve nut 30, and subsequent abutmentof compression sleeve 24 against inner end of gripping member 25.Because the gasket ring 18 is attached to the inner end of sleeve 24,that is also withdrawn and does not remain in the small diameter portionof socket 17.

As seen best in FIG. 2, when sleeve nut 30 is tightened over body 12,radially outstanding flange 42 of gripping member 25 lies adjacentshoulder 43 of nut 30. If a tensile load is applied to pipe 11 and body12 is fixed, any relative movement will initially impart more radialcompression to gripping member 25, but such movement (if any) will bevery small, and will be resisted by abutment of flange 42 againstshoulder 43.

With the invention, the body may be used with an insert and on astandard insert fitting as described in the aforesaid Australian PatentNo. 534452. It will be appreciated that the assembly may be sold withthe components in place and held captive while nevertheless retaining aclearance over the outer surface of pipe 11.

The second embodiment of FIGS. 3 and 4 illustrates how a pipe 11 ofouter diameter which may differ slightly in different standards may beaccommodated in a coupling or other fitting which embodies the featuresof this invention. The innermost portion of socket 17 is the same inFIGS. 3 and 4 as in FIGS. 1 and 2, and the effective portion of pipe 11is extension 11a of a transition spigot 46, which enters socket 17 andis of constant diameter with a range of transition spigots, whichhowever have varying diameter barbed tails each insertable into an endof a pipe with an interference fit, of one of a number of pipes 11 ofvarious diameters which differ by only small amounts. Thus it is notnecessary to produce or stock so many fittings to accommodate pipes ofsimilar but not identical diametral dimension produced to differentstandards.

I claim:
 1. A polymeric pipe coupling comprising:a) a body having anexternal thread, axially aligned annular inner surfaces and a radiallyextending axially outwardly facing inner end surface defining a socketwithin the body, said axially aligned annular inner surfaces being oflarger diameter at an outer end of said socket than inwardly thereof; b)a nut having an internal thread adjacent an inner end thereof engagingsaid body external thread, the nut also having a radially extendingaxially inwardly facing internal abutment surface between ends of saidnut and an axially outwardly converging internal circular surfacebetween said abutment surface and another end of said nut, the nutfurther having a sleeve retention surface adjacent said inwardly facinginternal abutment surface; c) an annular compression sleeve having afirst abutment surface at an outer end co-operable with said nutabutment surface, the sleeve also having a second abutment surfacespaced axially inwardly from the first said abutment surface andco-operable with said outer end of said body upon tightening of saidnut, the sleeve further having a retention surface co-operable with saidnut retention surface to be loosely retained by said nut; d) a resilientgasket ring secured to an inner end of said sleeve; e) a deformablegripping member having an axially outwardly converging outer surfacecomplementary to said axially outwardly converging internal nut surface,the gripping member having an internal surface with barbs extendingradially inwardly therefrom, f) internal diameters of said socket innerend, sleeve and gripping member all being only slightly greater than anexternal diameter of a pipe to which said coupling is securable, suchthat an end of such pipe is freely insertable through said grippingmember, sleeve and gasket ring into said socket inner end, andtightening of said nut over said external thread causes axial movementof said sleeve, sealing engagement of said gasket ring with said bodyand such pipe, and radially inward deformation of said gripping membersuch that said barbs clamp such pipe; and, g) said retention surfaces ofsaid nut and said annular compression sleeve being loosely engagingaxially outwardly diverging surfaces which retain said sleeve to saidnut as a preliminary assembly.
 2. A polymeric pipe coupling according toclaim 1 wherein said annular compression sleeve has a radial flange atits outer end, the flange having an axially inwardly facing abutmentsurface and an axially outwardly facing abutment surface arranged in aconfiguration whereby said axially inwardly facing abutment surfaceabuts said outer end of said body and said nut axially inwardly facinginternal abutment surface abuts said flange axially outwardly facingabutment surface when said nut is tightened, in turn controlling degreeof compression of said resilient gasket ring, and wherein said retentionsurface of said annular compression sleeve is located between saidaxially inwardly facing and axially outwardly facing abutment surfaces.3. A polymeric pipe coupling according to claim 1 wherein said socketdefining annular inner surfaces comprise a radially extending axiallyoutwardly facing abutment shoulder at said socket inner end, saidannular inner socket surfaces being generally cylindrical, an axiallyaligned outer socket surface being of larger diameter than the diameterof said inner socket surface and including a further axially alignedintermediate annular surface axially between said inner and outer socketsurfaces and of diameter between said inner and outer socket surfacediameters, and terminating in a generally annular planar surface,against which said gasket ring seals upon said tightening of said nut.4. A polymeric pipe coupling according to claim 3 wherein the diameterof said axially aligned outer socket surface exceeds the outer diameterof said resilient gasket, and the diameter of said axially alignedintermediate annular surface is less than said gasket outer diameter,but of sufficient dimension to permit axial traverse of said sealingring from said outer socket surface and into sealable engagement withsaid intermediate annular planar surface of said socket.
 5. A polymericpipe coupling according to claim 1 wherein said deformable grippingmember is a split ring and at least certain of said barbs each have asaw-tooth shape in cross-section.
 6. A polymeric pipe couplingcomprising:a) a body having an external thread and annular innersurfaces defining a socket within the body having a larger diameter atan outer end than at an inner end of said socket; b) a nut having aninternal thread at an inner end thereof engaging said body externalthread, the nut also having an inwardly facing internal abutment surfacebetween ends of said nut and an outwardly converging internal circularsurface between said abutment surface and an outer one of said nut ends;c) an annular compression sleeve having an abutment surface at its outerend co-operable with said nut abutment surface, and a resilient gasketsecured to its inner end; said abutment surfaces of said nut and saidannular compression sleeve being loosely engaging axially outwardlydiverging surfaces which retain said sleeve to said nut as apreliminary, assembly ; e) a deformable gripping member having anoutwardly converging outer surface complementary to said outwardlyconverging internal nut surface, the gripping member having an internalsurface with a first set of barbs extending radially inwardly therefrom;f) wherein said socket defining surfaces comprise an abutment shoulderat said socket inner end, said annular inner socket surfaces beinggenerally cylindrical, an outer socket surface being of larger diameterthan the diameter of said inner socket surface and including a furtherintermediate annular surface axially between said inner and outer socketsurfaces and of diameter between said inner and outer socket surfacediameters, and terminating in a generally planar annular surface,against which said gasket ring seals upon tightening of said nut; g)further comprising a hollow transition spigot having at one end a hollowtail insertable with an interference fit to sealably engage into a pipe,the tail having a second set of barbs projecting outwardly therefrom,the spigot also having a portion adjacent another end thereby forming apipe extension which is compatible in diameter with said gripping memberto be freely insertable through said griping member, sleeve and intosaid socket inner end, and wherein tightening of said nut over saidexternal thread causes axial movement of said sleeve, sealableengagement of said gasket ring, said body and said pipe extension, andradially inward deformation of said gripping member such that barbs ofeach of said sets grip an inserted pipe said hollow transition spigothaving a diameter of said one end slightly greater than the internaldiameter of said pipe to form an interference fit.